Cathode ray tube and circuit



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GATHODE RAY TUBE AND CIRCUIT Filed March 15, 19.40 2 Sheets-Sheet 1(WIMP .4. 0. INPUT l3 aurpur ELECTRON BEAM INVENTOR. CLARENCE w HA NSELLATTORNEY.

Wm. 22, 1942. c. w. HANSELL 2,305,617

CATHODE RAY TUBE AND CIRCUIT Filed March 15, 1940 2 Sheets-Sheet 2 MW WINVENTOR.

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Patent 1942 ctrr Clarence Hall, Port .iefl'erson, N. Y assignor to RadioCorporation of America. a corporation of Delaware Application in,

. l5 Elaims.

This invention relates to improvements in cathode ray type electrondischarge devices and circuits therefor, and particularly concerns acathode ray device wherein an electron stream is shifted between a pairof electron collecting elecgrtfies under the influence of a deflectingelectric An object of the present invention is to provide an electronicamplifierol alternating currents which is extremely sensitive and has alarge ratio of controlled current and power to control current andpower.

Another object is to provide means for continuously increasing theangular deflection of an electron beam during the interval of travelfrom the cathode to the electron collecting electrode.

A further object of the present invention is to provide an electricfield for a cathode ray tube oil such configuration that it continuouslyacts on the electron beam over the major part of its'path of travel toincrease the initial deflection, and is only effective after thebeam hasbeen pulled ofi center.

A still further object is to provide a high frequency amplifier of theelectron beam type which has a greater sensitivity and greater controlof the current and power in the tube than conventional beam type tubesnow in use.

These objects and others will be more readily understood from a readingof the following description which is accompanied by drawings, wherein:

Figs. 1, ii and 6 illustrate different embodiments oi cathode ray tubesembodying the principles of the invention;

Figs. 2 and 5 are 'iragrnentary cross section views of Figs. 1 and i,respectively, showing the positioning of the most important electrodesoi the tubes and the electric field distribution thereioetween; and

Fig. 3 illustrates a cross-section of a modification of the tube oi Fig.1.

Throughout the figures the same or equivalent parts are represented bythe same reference nuinerals.

Referring to Fig. l in more detail, there is shown a cathode ray tubehaving within an evacuated envelope i an electron emitting cathode i, adeflecting plate electrode 3, a pair of rod-like electrodes i, isymmetrically positioned on opposite sides of the axis oi the tube, ametallic cylinder 5 surrounding the rod electrodes t, t, a pair ofelectron collectors or anodes t, t. and an axially positioned shield orscreen plate ch is, 1940. Serial No. 824.0%

(or. sac-2r) 1 of unidirectional potential it.

electrode i for shielding the anodes from each other.

The cathode ray tube is illustrated as being used for the amplificationof alternating currents, and has connected to it a suitable inputcircuit 8 extending to a source of signal waves to be amplified, notshown, and coupled via a parallel tuned circuit 9 to, the deflectingplate electrode 8. The rod-like electrodes i, d are each maintained at arelatively high positive potential with respect to'the cathode overindividual paths which include leads it, it, resistors ill, ill andopposite'sides of a potentiometer ii to an intermediate point ofwhich'is connected 2. lead i2 extending to the positive terminal of asource The anodes t, t are connected to the opposite terminals ofpotentiometer it over individually tunable output circuits ii, ii, thelatter being coupled by means of transformer i l to a suitable commonutilization circuit, not shown. The shield i, cylinder i and deflectingelectrode i are maintained at substantially the same positive potentialrelative to the cathode although at a less positive potential than therods t, i and anodes it, t.

The electric field distribution between the rods ii, i and cylinder t isshown in Fig. 2 which illustrates a cross-section of the vacuum tube ofFig. 1 along the dash lines 22. In Fig. 2, the electron beam whichnormally passes along the axis of the tube in the absence of deflectingpotentials, is shown by the dotted circular lines in the center of thecylinder. It should be noted that the electric field is substantiallyzero along the axis of the cylinder but increases rapidly between theaxis and the rods i, i. Electrons traveling through the cylinder whichare not on the axis will therefore be deflected by the electric'flelcltoward one or the other of the rod-like electrodes ii, ii. It will beevident that when the electron beam travels down the axis or thecylinder i, its center line will be substantially unafiected by theelectric field within the cylinder. However, if the the beam isdeflected ofl the axis toward one or the other of the rod-likeelectrodes t; t, the beam will be acted on by the electric fleld toincrease the deflection. Putting it another way. the initial deflectionof an electron toward one rod i will cause a greater movement towardsaid one rod by virtue of the positive potential on this rod. Theoppositely located rod i will not have an exact counter attraction onthis electron because of the field distribution shown in Fig. 2. As soonas the electron is pulled or drawn ofl the axis or center toward one rodelectrode i, the

force on this electron increases in a direction toward the said one rod.

In the operation of the device'and circuit of Fig. 1, the input energyon line t, which is to be amplified, is impressed on tuned circuit 9 andcauses deflecting electrode 3 to move the electron beam up or downtoward one of the rodlilre electrodes l. The initial deflection of thebeam produced by the electrode 3 will then be increased by the action ofthe electric field in the, manner described above, and the greatlyincreased deflected beam will impinge predominantly on that one of theanodes t which is nearest the rod l toward which the beam is moving. Theelectrodes t, d are, of course, of such length and the potentialsapplied are of such value that the electrons do not impinge on theseelectrodes but pass over the ends to be collected by anodes ii, t. Atextremely high frequencies there may be several waves within thecylinder at any instant of time. These waves start with small amplitudesnear the control electrode t and then grow to be much larger wavesbefore the output end of the cylinder is reached.

As an illustration of the increase in deflection of the beam obtainableby the tube of the invention, given by way of example only for purposesof exposition and not by way of limitation,

if the control electrode potential on 3 can produce 0.01 centimeterinitial deflection then the electric field traversed by the beam mightincrease this deflection to say 0.1 centimeter or more. Therefore, thecorresponding gain in amplification may he, say, to 1 in current or 100to 1 in power, or more. This increase in amplification is effectivesubstantially independently of the frequency of the currents to beamplified.

The separate connections i5, It to the rod-like electrodes-and thepotentiometer arrangement ii enables the direct current or low frequencypotentials derived from the anodes 6, ii, to control the average ordirect current potentials on the rods d, d in a direction to keep themean position of the center of the electron beam properly centered. Asan illustration, assuming that one anode ii tends to take more directcurrent than the other anode, then there will be a greater current flowand IR drop in one-half of the potentiometer ii and a correspondinglowering of the 'positive potential applied to that rod ii directlyassociated with the anode drawing the greater direct current. Thefrequency response of this beam centering arrangement is such that itdoes not affect deflections of the beam at the operating frequency butonly prevents deflections at lower frequencies and steady statedefiections.

If desired, the cylinder 5 maybe flattened to take the approximate formof an ellipse in the manner shown in Fig. 3 without departing from theprinciples of the invention. It will be noted that the fielddistribution of Fig. 3 is substantially the same as that of Fig. 2.

As a practical matter, the cylinder of Fig, 1 and the ellipse of Fig. 3can be dispensed with and two flat plates i8, i8 substituted therefor.One such arrangement, given by way of example, is shown in Fig. 4. Thefield distribution between rod-like electrodes l, i and the plates isshown in Fig. 5 which represents a cross-section of the tube of Fig. 4along the line 55. It will be evident that the field distributions ofFigs. 2, 3 and 5 are substantially similar and will cause similareffects on the electron beam. In Fig. 4, there is shown a tubularaccelerating electrode it which has integral therewith a circular shieldI? for removing stray electrons. The electrode Ill and plates Iii, iiihave suitable positive polarizing potentials applied thereto over leads2! and 22 which potentials may be of substantially the same valuealthough lower than the positive potential applied to rods l, ii andanodes 6', t. The anodes 6, t are shown as being hollow or cupshaped tominimize the effects of secondary emission and to insure that secondaryelectrons do not extend beyond the confines of the anode structure. ofcourse, any other type of anode structure, such as a plate, can be usedinstead. The shield 'i' is somewhat different in form from shield i ofFig. 1. Shield 1' is maintained at a positive potential relative to thecathode, and is composed of a central plate part IQ for enabling axiallytravelling electrons to impinge thereon and upper and lower apertures 20for enabling the deflected electrons to pass through the shield and toimpinge on the anodes. The operation of the system of Fig. 4 insofar asthe present invention is concerned is substantially identical with thatof Fig. 1.

Although rod-like electrodes ti, l of Figs. 1 to ii have been shown asbeing parallel to each other and perfectly straight, they can bearranged at a diverging angle and, if desired, curved slightly outwardfrom the axis of the device to correspond to the shape of the path ofthe beam.

Fig. 6 shows a cathode ray tube in accordance with another embodiment ofthe invention, which functions by means of a magnetic field, instead ofthe electrostatic fields of Figs. 1 to i. In Fig. 6 there is provided afield coil 23 which replaces the cylinder, plates and rod-likeelectrodes of the other figures. Coil til is energized by a source ofunidirectional potential it and provides a desired non-uniformfan-shaped magnetic field throughout the space traversed by the beam inthe manner indicated by the dash lines, the intensity of which increasestoward the point of origin of the beam. It will be observed from aninspection of Fig. 6 that the direction of the field changes accordingto the distance from the axis. The field coil 23 provides the sameresult as the electrostatic field of Figs. 1 to 5.

I prefer to call the circuit of my invention a "growing wave amplifierbecause the control potentials on electrode it cause the electron streamto deflect in such a way as to produce a wave in the stream whichtravels along the length of the tube with a velocity equal to thevelocity of electrons in the stream. This wave starts with smallamplitude near the deflecting electrode and grows to be a very muchlarger wave before the output end of the tube is reached.

There is a crude analogy between the effect of the electric field in thecylinder increasing the wave amplitude and an effect which might beproduced with surface waves on water. If we passed a strong current ofair parallel to the surface of water in a long trough, this air wouldgive little if any energy to the water so long as the water surface wasperfectly smooth. However, if we deliberately produced small waves inthe water at the end of the trough from which the air comes, thepresence of the waves would provide a coupling between water and airwhich would cause the waves to grow in amplitude as they travelled downthe trough. In this water wave case we have another example of means tocause waves deliberately produced to grow in strength with passage oftime and distance but,

at all times, the waves are controllable by the input wave power.

It should be understood that the invention is not limited to the precisearrangements of parts shown and described since various modiflcationsmay be made without departing from the spirit and scope of theinvention. For example, the cylinder of Fig. 1 or the ellipse of Fig. 3can be dispensed with and at least a large'part of the envelope made ofmetal, or the inner surface oi the glass envelope can be coated withmetal to simulate the metallic cylinder or ellipse.

What is claimed is:

l. The method of influencing a stream of electrostatically chargedparticles which comprises surrounding the stream over the greaterportion of its travel with an electric field whose transverse value issubstantially zero along the normal axis of the stream and whoseintensity .increases in at least one direction with distance from saidaxis, whereby an initial deflection of said stream in said one directionwill produce an increase of deflection in the same direction as theelectrons travel through said field.

2. In an electrical discharge device having means for producing a streamof charged particles alon the axis of said device and means responsiveto deflection of the stream in a particular plane, means for producing atransverse electric field around said stream over the greater portion oftravel of said stream and whose value is substantially zero along thesaid axis and which increases rapidly with distance from said axis alongsaid plane, and means adjacent said stream near the beginning of itstravel and responsive to alternating currents for deflecting said streamin said plane, whereby a deflection of said stream caused by said lastmeans will increase in size as said stream passes through said field.

3. In an electrical discharge device having a cathode for producing anelectron beam along the axis of said device, a pair of anodessymmetrically arranged on opposite sides of said axis, a deflectingelectrode adjacent said beam and located between said cathode and saidanodes, and means also located between said cathode and said anodes forproducing a substantially transverse electric fieldwhose value issubstantially zero along said axis and which increases rapidly in apredetermined plane at right angles to said axis, said means including apair of rod-like elec-. trodes symmetrically positioned in said plane onopposite sides of said axis, and connections for maintaining saidrod-like electrodes at positive potentials relative to said cathode,said deflecting electrode functioning to deflect said beam in said planetoward one or the other of said rod-like electrodes.

4. In an electrical discharge device having a cathode for producing anelectron beam along the axis of said device, a pair of anodessymmetrically arranged on opposite-sides of said axis,

arranged with respect to the axis of said device,

connections from said rod-like electrodes and said tubular surface tosources of unidirectional potential for maintaining said elements atsuitable polarizing potentlals, said deflecting electrode functioning todeflect said beam in said plane toward one or the other of said rod-likeelectrodes. I l a 5. Apparatus in accordance with claim 4, characterizedin this that said hollow tubular surface is a cylinder.

6. Apparatus in accordance with claim 4, characterized in this that saidhollow tubular surface has the form of an ellipse with its flat sidesparallel to said predetermined plane.

7. In an electrical discharge device having a. cathode for producing anelectron beam along the axis of said device, a pair of anodessymmetrically arranged on opposite sides of said axis, a deflectingelectrode adjacent said beam and located between said cathode and saidanodes, and means also located between said cathode and said anodes forproducing an electrostatic field whose value is substantially zero alongsaid axis and which increases rapidly in a predetermined plane at rightangles to said axis, said means including a. pair of rod-like electrodessymmetrically positioned in said plane on opposite sides of said axis,and parallel plate electrodes also symmetrically position on oppositesides of said axis but in planes parallel to the plane containing saidrod-like electrodes, said plate electrodes being substantiallycoextensive in length with said rod-like electrodes. and con nectionsfrom said rod-like electrodes and said plate electrodes to sources ofunidirectional potential for maintaining said electrodes at suitablepolarizing potentials.

8. In an electrical discharge device having a cathode for producing anelectron beam along the axis of said device, a pair of anodessymmetrically arranged on opposite sides of said axis, a deflectingelectrode adjacent said beam and located between said cathode and saidanodes, and means also located between said cathode and said anodes forproducing an electrostatic field whose value is substantially zero alongsaid axis and which increases rapidly in a predetermined plane at rightangles to said axis, said means including a pair of rod-like electrodessymmetrically positioned in said plane on opposite sides of said axis,one of said rod-like electrodes being on the same side of said axis asone anode while the other rod-like electrode is on the same side of saidaxis as the other anode, a potentiometer having opposite terminalsconnected to said anodes and an intermediate point on said potentiometerconnected to the positive terminal of a source of unidirectionalpotential, a connection from a negative terminal of said source to saidcathode, and a connection from each of said rodlike electrodes to thatterminal on said potentiometer to which the correspondingly locatedanode is connected, whereby the unidirectional potentials on said anodesautomatically control the average direct current potential on saidrodlike electrodes for maintaining the normal direction of said beamalong said axis in the absence of deflecting potentials.

9.-Apparatus in accordance with claim 8, including a shielding platepositioned between said anodes and in the plane of said axis.

10. The method of influencing a stream of electrically charged particleswhich comprises surrounding the stream over the major part of its travelwith an electric field which is constant 11. In an electrical dischargedevice having a cathode for producing an electron beam along the axis ofsaid device, a pair of anodes symmetrically arranged on opposite sidesof said axis, a deflecting electrode adjacent said beam and locatedbetween said cathode and said anodes, and means located between saiddeflecting electrode and said anodes for producing a substantiallytransverse electric field whose value is substantially zero along saidaxis and which increases rapidly in a predetermined plane at rightangles to said axis, saidmeans including a pair of rod-like electrodessymmetrically positioned in said plane on opposite sides of said axis,and connections for maintaining said rod-like electrodes at positivepotentials relative to said cathode, said deflecting electrodefunctioning to deflect said beam in said plane toward one or the otherof said rod-like electrodes.

12. In an electrical discharge device, means for producing a beam ofelectrons substantially along a line through the center of said device,and mean including a pair of electrically-conducting surfaces onopposite sides of said beam and maintained at a predeterminedunidirectional potential for producing an electric fleld around saidbeam for a substantial portion of the path of travel of said beam andwhich fleld has the following characteristics: (a) is substantially zeroalong the axis of said beam; (b) is effective only after the beam hasbeen deflected from said axis; and (c) has a component in one directiontransverse to the axis which increases with distance from said axis, andan electron deflecting element positioned near the beginning of the pathof travel of said beam through said electric field, whereby the electricfleld continuously act to increase the initial deflection of said beam.

13. In an electrical discharge device, means including a cathode forproducing a beam of electrons substantially along a line through thecenter of said device, and means near said cathode for deflecting saidbeam, and means for enhancing the deflection caused by said deflectingasoaeir means, said deflection enhancing means, including a pair ofsurfaces on opposite sides of said beam and maintained at apredetermined unidirecticnal potential, producing an electric fieldaround said beam for a substantial portion of the path of travel of saidbeam and which flld has the following characteristics: (a) issubstantially zero along the axis of said beam; (11) is edective onlyafter the beam has been deflected from said axis; and (c) has a.component in one direction transverse to the axis which increases withdistance from said axis.

14. In an electrical discharge device having means for producing a beamof electrons, a pair of anodes symmetrically positioned on oppositesides of the normal path of travel of said beam when said beam isundeflected, means for shielding said anodes from one another, adeflecting element adjacent said beam and located between said cathodeand said anodes, and means located between said deflecting element andsaid anodes for producing a substantially transverse electric fleldwhose value is substantially zero along said axis and which increasesrapidly in a predetermined plane at right angles to said axis, saidmeans including a pair of rod-like electrodes symmetrically positionedin said plane on opposite sides of said axis, and connections formaintaining said rod-like electrodes at positive potentials relative tosaid cathode, said deflecting element functioning to deflect said beamin said plane toward one or the other of said rod-like electrodes.

15. In a cathode ray device, means including a cathode for producing abeam of electrons, means for deflecting said beam,- and means forenhancing the deflection caused by said deflecting means comprising apair of spaced metallic elements symmetrically positioned and oppositelydisposed with respect to the normal path of travel of said beam andextending over the major portion of the path of travel of said beam, anda pair of spaced metallic surfaces symmetrically positioned andoppositely disposed with respect to said beam, but located on a line atright angles to an imaginary line Joining said pair of elements, saidpair of surfaces having a length at least as long as said pair ofelements, said surfaces being maintained 7 at a potential which ipositive relative to said cathode but less positive than the'potentialon said pair of elements.'

CLARENCE W. HANSELL.

